DISSERTATION RESEARCH: Nutrient cycling and distribution over multiple scales in a Kenyan savanna as mediated by an acacia-ant mutualism

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In Kenya, a common Acacia tree in effect employs an army of ants to defend its leaves from being eaten by giraffes, elephants, and other large herbivores. In exchange for this protection, the trees provide the ants with nesting space and nectar for food. This mutually beneficial interaction between Acacia trees and ants may involve more than just protection, though: preliminary data suggest that at least some of the ants may also fertilize the trees in which they live. The objective of this research is to examine how nutrients are exchanged between ants and trees, to determine how this interaction might affect soil nutrient availability, and to investigate the effect of the disappearance of large mammals on these processes. To address these questions, this study will combine a nitrogen-tracing experiment with soil sampling to track ant-derived nutrients, in addition to using long-term mammal-exclusion plots to investigate the influence of mammals.This study incorporates work directly applicable to land management in eastern Africa: loss of native browsers, a significant problem across much of Africa, could alter the mutually beneficial interaction between ants and plants, in turn affecting soil fertility and forage quantity and quality. This research will employ a Kenyan research assistant as well as involve undergraduates from Stanford University. Results of applied aspects of the research will be communicated to local land owners and managers through local publications, talks, and conversations.